Analyze an SDS

DOT Division 4.3: Dangerous When Wet

Division 4.3 is the DOT division for materials that are dangerous when wet: materials that, in contact with water, can become spontaneously flammable or give off flammable or toxic gas in dangerous quantities.

How it is defined

  • The hazard is triggered by water, including moisture in the air, rain, sprinkler water or wet equipment.
  • The gas released is usually hydrogen or acetylene, though others are possible.
  • Packing groups reflect how vigorously the material reacts.

Summary of 49 CFR Parts 171 to 180. The regulations and the Hazardous Materials Table (49 CFR 172.101) control any shipment.

Label and placard

Colors
Blue background, white or black flame
Symbol
Flame

A blue diamond with a flame and the number 4. Placards may carry the words DANGEROUS WHEN WET.

Packing groups

PG I (reacts violently), PG II (reacts readily) and PG III (reacts slowly). How packing groups work.

Common examples

  • Sodium and potassium metal
  • Calcium carbide
  • Lithium metal
  • Some metal hydrides

How it relates to GHS

Corresponds to GHS substances which, in contact with water, emit flammable gases (Categories 1 to 3).

DOT classes and GHS classes are assigned under different rules, so a product can have different severity labels in each. See also all GHS hazard classes.

Safe handling reminders

  • Keep dry and store away from water lines and sprinklers where safe to do so.
  • Use dry sand, class D extinguishers or the media listed in Section 5; never use water.
  • Handle under inert gas or oil if directed.

Where to find it on an SDS

Section 14 shows Division 4.3, UN number, packing group and ERG guide number. NFPA diamonds often show a crossed W. Look in Section 14: Transport information. Hazard classification for the workplace is in Section 2. You can also see how a UN number points to a response guide on the UN and NA numbers page.

Frequently asked questions

What is Division 4.3?

Division 4.3 covers DOT materials that are dangerous when wet, meaning they react with water to produce flammable or toxic gas. Sodium, potassium and calcium carbide are examples.

General reference only. It does not replace the supplier's SDS or the current federal regulations.